Principles Related to Practical Chemistry · Question 54

The metal ion whose electronic configuration is not affected by the nature of the ligand and which gives a violet colour in non-luminous flame under hot condition in borax bead test is

1. Cr3+
2. Ti3+
3. Ni2+
4. Mn2+

Answer

(3) Ni2+

Solution

Octahedral configurations:

Cr3+ (3d3): t2g3; Ti3+ (3d1): t2g1; Ni2+ (3d8): t2g6eg2 — the same with weak and strong field ligands.

Mn2+ (3d5): t2g3eg2 (weak field) or t2g5 (strong field) — affected by the ligand.

Borax bead test in the non-luminous (oxidising) flame: Ni gives a violet bead when hot (reddish-brown when cold); Cr gives a green bead; Mn gives an amethyst bead both hot and cold.

The ion is Ni2+.

Answer: (3)